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        FEM Simulation and Test Verification of PD Ultrasonic Signal Propagation in a Power Transformer Model

        Zan Wang,Chaofei Gao,Liwei Zheng,Jikun Ren,Wei Wang,Yushuai Zhang,Shijie Han 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.1

        Ultrasonic signals will be generated when partial discharge occurs in internal insulation faults in large oil immersed power transformers: because the ultrasonic signal has strong anti-interference ability and has no direct electromagnetic contact with the equipment, it is widely used in transformer fault detection and positioning. In this paper, the fi nite element method (FEM) is used to simulate the ultrasonic signal in a 35 kV power transformer. The infl uence of transformer case on ultrasonic signal propagation is considered, and the propagation law of the ultrasonic signal inside the transformer is obtained. Fabry–Pérot (F–P) fi bre acoustic sensors with a centre frequency of 28 kHz were fabricated. A partial discharge detection test was carried out in a 35 kV transformer winding model using the F–P sensors. The test results show that the ultrasonic waveform detected by the F–P sensors are in good agreement with the simulation results, and the propagation of the ultrasonic wave inside the transformer is verifi ed. It lays a foundation for detecting and locating PDs in power transformer by F–P acoustic sensors.

      • KCI등재

        Polycyclic aromatic hydrocarbon emissions of non-road diesel engine treated with non-thermal plasma technology

        Chaochen Ma,Jianbing Gao,Shikai Xing,Liwei Sun,Jiangquan Liu 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.12

        Non-road diesel engines are important polycyclic aromatic hydrocarbon (PAH) sources in the environment due to their high emission concentration compared to on-road diesel engines. Particle- and gas-phase PAH concentrations of a non-road diesel engine were investigated. Non-thermal plasma (NTP) as an effective after-treatment technology was used to reduce PAH emissions. The results showed that particle-phase PAH concentrations were 329.7 μg/m3, 3,206.7 μg/m3, and 1,185.7 μg/m3 without the action of NTP at three different engine loads respectively. Relatively low concentrations were measured for gas-phase PAHs. Excellent linearity was shown for particle-phase with total PAH concentrations both with, and without, NTP. The gas-phase PAH concentrations linearly increased with engine load without NTP. The five most abundant compounds of PAHs were among low molecular weight (LMW) and medium molecular weight (MMW) compounds. Total PAH cleaning efficiency was beyond 50% when treated with NTP at the three different engine loads. We hypothesized that naphthalene (Nap) concentrations increased greatly at 60% and 80% engine loads because it was produced within the plasma zone by decomposition of high molecular weight (HMW) PAHs. The PAHs content of particulate matter (PM) aggregation at 60% load was approximately three times higher than at 40% and 80% loads. High correlation values were observed for MMW PAHs with total PAH concentrations. Correlations of PAH concentration reduction could be important to clarify the PAH reduction mechanism with NTP technology.

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        Efficient Constitutive Expression of Cellulolytic Enzymes in Penicillium oxalicum for Improved Efficiency of Lignocellulose Degradation

        ( Pankajkumar Ramdas Waghmare ),( Pratima Pankajkumar Waghmare ),( Liwei Gao ),( Wan Sun ),( Yuqi Qin ),( Guodong Liu ),( Yinbo Qu ) 한국미생물생명공학회(구 한국산업미생물학회) 2021 Journal of microbiology and biotechnology Vol.31 No.5

        Efficient cellulolytic enzyme production is important for the development of lignocellulose-degrading enzyme mixtures. However, purification of cellulases from their native hosts is time- and labor-consuming. In this study, a constitutive expression system was developed in Penicillium oxalicum for the secreted production of proteins. Using a constitutive polyubiquitin gene promoter and cultivating with glucose as the sole carbon source, nine cellulolytic enzymes of different origins with relatively high purity were produced within 48 h. When supplemented to a commercial cellulase preparation, cellobiohydrolase I from P. funiculosum and cellobiohydrolase II from Talaromyces verruculosus showed remarkable enhancing effects on the hydrolysis of steam-exploded corn stover. Additionally, a synergistic effect was observed for these two cellobiohydrolases during the hydrolysis. Taken together, the constitutive expression system provides a convenient tool for the production of cellulolytic enzymes, which is expected to be useful in the development of highly efficient lignocellulose-degrading enzyme mixtures.

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        Nonenzymatic Glucose Biosensor Based on NiNPs/Nafion/graphene Film for Direct Glucose Determination in Human Serum

        Parviz Sukhrobov,Sodik Numonov,Sanshuang Gao,Xamxikamar Mamat,Thomas Wagberg,Yufen Guo,Liwei Liu,Guangzhi Hu 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.7

        This study describes a type of novel nickel nanoparticles (NiNPs) decorated on Nafion-graphene composite film by using the electrochemical deposition method. It was used to fabricate electrochemical biosensors for sensitive nonenzymatic glucose detection. Compared with the Nafion–graphene film and NiNPs-modified glassy carbon electrode (NiNPs-GCE), the NiNPs/Nafion/graphene/GCE showed the best electrocatalytic activity towards glucose oxidation in alkaline medium. The NiNPs/Nafion/graphene/GCE at an applied potential of +0.55V in a linear range of 1–200 μM presented a high sensitivity of 3437.25 μA·mM -1 cm -2 with coefficient of correlation R2 = 0.999; and in a linear range of 200–10 800 μM it performed the best sensitivity of 2848.6 μA·mM -1 cm -2 with coefficient of correlation R2 = 0.995 towards glucose oxidation. For a concentration up to 200 M, a linear range was obtained with a limit of detection of 0.6 μM (signal to noise = 3) and as much as 10 800 μM with a limit of detection of 0.82 μM (signal to noise = 3). The time of responses was about 1–1.5 s with the addition of 0.1–1mM glucose. In addition, NiNPs/Nafion/graphene/GCE also has a high anti-interference ability toward common oxidative interfering species, such as uric acid, ascorbic acid and dopamine. More importantly, NiNPs/Nafion/graphene/GCE was successfully used for the determination of glucose concentration in human serum samples in comparison with a local hospital. The NiNPs/Nafion/graphene/GCE exhibited high sensitivity, low working potential, good stability, excellent electrical properties, enhanced selectivity and fast amperometric responses to glucose oxidation. Thus, as a nonenzymatic sensor, it is promising for future glucose determination development.

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